Thread: Stroker SBC's using 5.6 400 rods

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.030 or .040 over 350 block with using the over sized 350 piston and a 3.75 stroke and the stock 400 rods which are 5.6.Comments or input??

Yes it is kind of the old school of doing things.

Originally Posted by 1gary

.030 or .040 over 350 block with using the over sized 350 piston and a 3.75 stroke and the stock 400 rods which are 5.6.Comments or input??

Yes it is kind of the old school of doing things.

Most fellows talk it down because of rod angularity which puts more force on the piston skirt against the cylinder wall and the other problem of crank counterweight to piston skirt clearance, but hey, the GM engineers designed the darned thing originally with those short rods. I wouldn't be so concerned personally about the angularity, but you have to clearance for the skirt to counterweight thing. I have carved piston skirts for clearance on my personal builds before and found that if I get the weight the same on all of the pistons, it works out fine. There may be some interference between some lobes of the cam and some of the rod bolts. Either grind on the bolts or use a reduced base circle cam for clearance. You don't need much clearance, just check it on your mock-up with the tip of a tie-wrap. Also, there may be a little interference at the pan rail with the big end of the rod, but a little grinding will take care of that. Again, use the thin tip of a tie-wrap to check clearance. A miss is as good as a mile. I'm sure you know you'll have to reduce the main bearing journal diameters on the crank also. As far as the short rod making less power than a longer rod, Iskenderian says it just ain't so. He says that because the piston parks for an instant longer at the bottom with a shorter rod, you can leave the intake valve open another 1-2 degrees and pack the cylinder a little better to make more power than you could with a longer rod. Personally, I have never measured the difference, I just lean on the experts. Longer rod, the piston parks for an additional instant at the top of the bore. Shorter rod, the piston parks for an additional instant at the bottom of the bore.

yep you can do it but why? by the time you pay to have the crank mains ground down you can buy a new crank$180 that fits for about the same as a regrind. the time you pay to recon the short rods.new 5.7 are less then 190.a set new .claimer pistons that fit are 200. now if you get the machine shop work for free or near free then do it . it was done at one time as there was no parts like there is now as for the pistons the CH is the same as the 350 .but you may not find a cheap piston that would clear the counter weight of the crank so there alot of pissing around when its really not needed .but yes it was done and can still be just going to cost as much as if you pickup a claimer crank assemblie

What I have been reading about is guys buying stroker cranks and hanging 400 rods/350 pistons off them.

Originally Posted by 1gary

What I have been reading about is guys buying stroker cranks and hanging 400 rods/350 pistons off them.

Yeah, if you're absolutely broke and have a buddy at a machine shop who will cut the 400 mains for free, this approach should work out for you.
Here's the flip side: I have a great deal of respect for Pat and will have to agree with him on his take on this. Depending on the parts you use to build your 383, you could easily double the hp/torque of the 350 that you start with. Do you really want to do that with 40 year old parts?

Scat makes a cast STEEL 3.750" crank that is under 200 bucks.....
Here's the one for 2-piece seal and external balance....
SCAT Engine Components 910375 - Scat Cast Crankshafts - Overview - SummitRacing.com
Use a 400 damper and flexplate
Here's a decent set of rods, I'm sure Pat could do better, but here's a set that's affordable anyway....
5140 I-Beam Rods, Chev SB (LJ), 5.700", Press Pin-Competition Products
I couldn't find any decent pistons, but Pat probably has some on the shelf.

i get flyer.s all the time the claimer pistons . a good way to go the new speed pro hiper is nice for the money .as for the crank regrind i do not have a crank grinder but it cost over 120. for a re grind so i would bet it would cost me 170 just to re grind a old gm 400 crank that has seal cut in it? and has a unknown history?? not worth it.. the way i see it even if the crank was free. yes some 350 pistons may clear and some may not .not much fun finding this out after you buy them they do not clear ?

I still have my .030 roller block Howards crank,5.7 Scat rod.Icon piston.The next one will be a LS series engine for me.